Greeley takes a big step forward with the second in this new series (after Irish Gold, 1994) starring Nuala (""Noola"") Anne McGrail. The 20-year-old Irish immigrant is beautiful, psychic, a gifted singer, charmingly fey and now in Chicago. Specifically in Fr. Greeley's Chicago, peopled by large Irish-Catholic, Democratic families of overachievers. An exception is hero and narrator Dermot Michael Coyne, who has made an accidental killing on the Chicago Mercantile Exchange and retired, at 25, to write. He also moons over Nuala: they love each other but are not about to rush the relationship. As in Gold, there are two mysteries here, one modern, the other historical. The first involves recent robberies in Chicago's upscale art galleries that an an ambitious prosecutor links to an I.R.A. conspiracy; the second centers around the major psychic pain Nuala Anne has suffered at the site of a Civil War prison camp. As Dermot unearths the story of the Camp Douglas conspiracy to set Confederate prisoners free, Greeley uses a long (fictional) letter of real-life Letitia Walsh to tell the story of her Peace Democrat father's trumped-up arrest. Moving effortlessly between the (fictional) conspiracies of 1864 and 1995 Chicago, Greeley is at his top page-turning form, throwing in a few stinging words about racism and xenophobia and delivering a rousing defense of the Bill of Rights. When he's good, as he is here, Greeley is very, very good. (Nov.)